The present invention relates to a pre-impact alarm apparatus, more particularly to an alarm apparatus which can sense when a car in the process of backing up is about to impact with an obstacle, and can generate an audio-alarm to warn the driver that such a situation exists.
Pre-impact alarm apparatuses are widely used for sensing whether or not a car in the process of backing up is about to impact with an obstacle. FIGS. 1A and 1B show a car provided with a conventional infrared alarm apparatus B installed on its rear side. As shown in FIG. 1A, while the car is in reverse, the conventional infrared alarm apparatus can generate an infrared signal to sense an obstacle A within a certain distance and simultaneously generate an audio-alarm to warn the driver that such an obstacle exists. However, as shown in FIG. 1B, when the car wishes to parallel park on the roadside, especially in a space between two rather closely parked cars, a conventional infrared alarm apparatus B can not give an appropriate warning to the driver of an obstacle A due to the angle of approach of the car.